The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Plasma etching is frequently used in, for example only, semiconductor fabrication. In plasma etching, ions are accelerated by an electric field to etch exposed surfaces on a substrate. The electric field is generated according to RF power signals generated by a radio frequency (RF) generator of an RF power system. The RF power signals generated by the RF generator are precisely controlled to effectively perform the plasma etching.
An RF power system may include an RF generator, a matching network, and a load, such as a plasma chamber. The RF power signals are used to drive the load to fabricate various components including, but not limited to, integrated circuits (ICs), solar panels, compact disks (CDs), and/or digital versatile (or video) discs (DVDs). The load may include any of a number of elements or devices driven by an RF signal, including, but not limited to, the plasma chamber. The load may include broadband mismatched loads (e.g., cables with mismatched resistor terminations), narrowband mismatched loads (e.g., a 2-element matching network), and resonator loads.
The RF power signals are received at the matching network. The matching network matches an input impedance of the matching network to a characteristic impedance of a transmission line between the RF generator and the matching network. This impedance matching aids in minimizing an amount of power applied to the matching network in a forward direction toward the plasma chamber (“forward power”) and reflected back from the matching network to the RF generator (“reverse power”). Impedance matching also assists in maximizing forward power output from the matching network to the plasma chamber.
There are various approaches to applying the RF signal to the load. One example approach is to apply a continuous wave signal to the load. The continuous wave signal is typically a sinusoidal wave that is output continuously by an RF power supply to the load. In the continuous wave approach, the RF signal assumes a sinusoidal output, and the amplitude and/or frequency of the sinusoidal wave can be varied in order to vary the output power applied to the load. Another example approach to applying the RF signal to the load involves pulsing the RF signal, rather than applying a continuous wave signal to the load.